ADDITIONAL SYSTEM INFORMATION :
macOS Mojave 10.14.5 (MacBook Pro)

openjdk version "12.0.2" 2019-07-16
OpenJDK Runtime Environment AdoptOpenJDK (build 12.0.2+10)
OpenJDK 64-Bit Server VM AdoptOpenJDK (build 12.0.2+10, mixed mode, sharing)

A DESCRIPTION OF THE PROBLEM :
The method java.awt.GraphicsConfiguration#getBounds can throw a NullPointerException when disconnecting displays.

REGRESSION : Last worked in version 11.0.4

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Run the attached code on a MacBook Pro.

While that is running:
1) Plug in an external display to the laptop
2) Close the laptop lid
3) Unplug the external display
-> Exception is thrown here
4) Open the laptop lid

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
No exception is thrown
ACTUAL -
Exception in thread "main" java.lang.NullPointerException
at java.desktop/sun.awt.CGraphicsDevice.getBounds(CGraphicsDevice.java:116)
at java.desktop/sun.awt.CGraphicsConfig.getBounds(CGraphicsConfig.java:57)
at Main.main(Main.java:10)

---------- BEGIN SOURCE ----------
import java.awt.*;

public class Main {

    public static void main(String[] args) {
        while (true) {
            GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment();
            for (GraphicsDevice gd : ge.getScreenDevices()) {
                GraphicsConfiguration gc = gd.getDefaultConfiguration();
                gc.getBounds();
            }
        }
    }
}
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
Catch the exception and ignore it.

FREQUENCY : occasionally